The difference between the two fights was Dempsey ,he had shed the ring rust and was sharper.Tunney said he noticed he was a different animal as soon as he came into the ring, he wasnt listless and disinterested, he was more like the old Dempsey.Unfortunately for Jack his stamina and legs were not what they had been and he had essentially deteriorated into a 4 round fighter.
Yes, Dempsey footwork wasn't perfect. It was very instinctual way to fight, he actually didn't have good trainer at the beginning of his career. Still, with much faster legs he overwhelmed Gibbons because he was very quick on his feet. Without this quickness, he couldn't do anything more than just following Tunney.